NEWBIE Question: why my xtal coloured black and cant be used

Hello dead toram player, i am a new player.
I just buy xtal (mozto machina) from the board, but i didnt see the colour is black and i cant attach it to my equipment
how i attach or do i need to do something to use my black xtal

 

Mozto Machina xtal is for weapon (red)
Its the upgrade of Demon Gate :3
You need that (D.G) xtal first~
Like, put that xtal in weapon first, then attach Mozto.M to it~
All Grey xtals are upgrades :3 n need previous version to be used

 

hahaha, just knew it. thanks for the reply man. #UnmentionedHero